1. Field of the Invention
The present invention relates to a method of manufacturing a wire, particularly sawtooth wire for all-steel sawtooth wire card clothings, in which the surface of a wire-shaped intermediate product, such as a wire already provided with sawteeth, is smoothened in an electropolishing process carried out in an electrolyte bath containing an electrolyte; the invention also relates to an apparatus suitable for carrying out such methods.
2. Description of the Related Art
All-steel sawtooth wire card clothings are used, for example, in processing textile fibers into yarns, non-woven fabrics, or the like. The individual sawtooth wires of the all-steel sawtooth wire card clothings usually have a height of less than 2 mm and a width in the area of the tooth tips of 0.2 mm or less. For manufacturing such fine sawtooth wires, a wire-shaped initial material is usually initially subjected to one or more drawing processes, wherein different heat treatment processes may be carried out between the individual drawing processes in order to provide the already drawn wire at least partially again with its deformability. Following this preparation, the wire is usually provided with sawteeth in an appropriate punching device. The sawteeth produced by the punching process may also be hardened prior to or following the punching process. After the punching process, small punched brows remain on the surface of the sawtooth wires. In addition, impurities caused by the preceding processing steps may adhere to the surfaces of the sawtooth wires, such as scale, i.e., oxide residues, or dirt residues produced during the thermal treatment.
These residues on the sawtooth wires are harmful when the sawtooth wires are later used for processing textile fibers, particularly when using high-capacity machines, because individual fibers may adhere to the card clothing teeth and the card clothing as a result has an increased tendency to fill with fibers and impurities, such as, for example, steel parts or the like. For avoiding these disadvantages, sawtooth wires intended for manufacturing all-steel sawtooth wire card clothings are usually additionally cleaned and polished after the punching or hardening process. For this purpose, usually an electrolytic polishing plant is used. In the electropolishing process carried out with such an electrolytic polishing plant, material is removed from the surface of the anodically switched wire-shaped intermediate product, such as the wire already provided with sawteeth and/or hardened wire, by using a usually material-specifically selected electrolyte and an external direct-current source. This material is dissolved by the electrolyte, wherein the removal takes place without mechanical load acting on the workpiece, i.e., the wire-shaped intermediate product, and leads to a smoothening or flattening of the workpiece surface. Consequently, the electropolishing process in principal is the reversal of the galvanizing process. In contrast to mechanical removal methods, the flattening achieved in this matter starts in the microscopic range and, with increasing duration of the operation, includes larger structures which are rounded and flattened at their surface. As a result, the electropolished surface is characterized by smoothness and closed structure in the micro range and a residual waviness in the macro range which depends on the initial state, the electropolishing duration and the structure of the material.
When manufacturing sawtooth wires for all-steel sawtooth wire card clothings, such an electropolishing process is carried out by winding wire-shaped intermediate products in several layers onto a carrier and immersing the intermediate products for a predetermined time in an electrolyte bath containing a suitable electrolyte in which the electropolishing process is then carried out.
However, it has been found that the sawtooth wires obtained with the conventional methods have a surface property which varies over the length thereof, so that a satisfactory smoothness is not achieved in all areas of the sawtooth wire surfaces.
In view of these problems in the prior art, it is the primary object of the invention to provide a further development of the known methods by means of which a uniform surface property can be achieved, and an apparatus suitable for carrying out such methods.
With respect to the method, this object is met by a further development of the above-explained method which is essentially characterized in that a relative movement is produced between the electrolyte and the intermediate product during the electropolishing process in the electrolyte bath.
This solution is based on the finding that, in conventional immersion methods in which the wire-shaped intermediate product wound onto a body is immersed in an electrolyte, the electrolyte does not flow uniformly around all portions of the sawtooth wire. This has the result that the treatment does not take place uniformly, especially at the tooth surfaces, wherein, in particular when the wire-shaped intermediate product is wound in several layers onto the carrier, there is not sufficient contact between the electrolyte and the tooth tips in the interior of the resulting xe2x80x9cwire ringxe2x80x9d; this also leads to an insufficient tooth polishing. When using the further development according to the invention of conventional methods, on the other hand, a uniform treatment for all portions of the wire-shaped intermediate product immersed in the electrolyte bath is achieved, because the relative movement between the electrolyte and the intermediate product has the effect that the electrolyte flows uniformly around this intermediate product which, in turn, results in a uniform and homogenous treatment during the electropolishing process.
As can be gathered from the above explanation of the method according to the invention, the apparatus according to the invention for carrying out this method is essentially characterized in that it includes a device for producing a relative movement between an electrolyte contained in an electrolyte bath and the wire-shaped intermediate product immersed in the electrolyte bath.
It has been found particularly advantageous if the intermediate product is moved in the electrolyte bath during the electropolishing process. For achieving a particularly efficient continuous method, the electropolishing process is carried out by conveying the intermediate product through the electrolyte bath, preferably by pulling the intermediate product through the electrolyte bath by means of a conveying device arranged in the conveying direction of the intermediate product behind the electrolyte bath and acting on the intermediate product. For this purpose, the apparatus according to the invention preferably has a conveying device with two conveyor rollers having roller axes extending parallel to one another, wherein the wire-shaped intermediate product is clamped between these conveyor rollers and is pulled through the electrolyte bath by rotating the conveyor rollers.
When carrying out the continuous electropolishing process according to the invention, a treatment time which is sufficiently long for achieving a satisfactory treatment, while simultaneously ensuring a high processing speed in a relatively small electrolyte bath, can be achieved if the intermediate product is deflected within the electrolyte bath with a suitable deflecting device in order to increase the travel path traveled by the intermediate product in the electrolyte bath. As a result, even if the conveying speed is relatively high, its sufficiently long dwell time within the electrolyte bath is achieved, without excessively increasing the size of the electrolyte bath for this purpose.
It has been found particularly useful it the intermediate product travels essentially helically around a deflecting device arranged within the electrolyte bath and provided with at least one deflecting roller. The dwell time of the wire-shaped intermediate product in the electrolyte bath can be adjusted in dependence on the material properties of the intermediate product, such as the surface property after leaving the electrolyte bath, if the conveying speed is controlled in dependence on these material properties. Moreover, the effectiveness of the electropolishing method according to the invention can be further increased if the direct current intensity of the direct current source coupled anodically to the intermediate product received in the electrolyte bath is controlled in dependence on the material properties of the intermediate product, such as the surface properties after leaving the electrolyte bath.
It has been found particularly useful if the intermediate product is pulled by means of the conveying device from an uncoiling reel and, as traveling through the electrolyte bath, is placed on a coiling reel and is wound onto the coiling reel. For increasing the efficiency of the electropolishing method of the invention it has also been found useful if the intermediate product is initially mechanically cleaned before carrying out the electropolishing process; for this purpose, the intermediate product preferably travels through a stationary cleaning device. This mechanical precleaning can be carried out by means of brushes and/or washing discs and results in the removal of coarse unevenness, such as notches, scratches and marks or substantial burrs which can only be removed with great difficulties by means of an electropolishing process which constitutes a fine or very fine treatment.
The electropolishing process according to the invention is usually carried out with the use of sulfuric acid and phosphoric acid (35-45 %), wherein chromic acid is avoided as much as possible. The electrolyte bath may also contain various additives or brighteners. For ensuring a problem-free further processing of the wire-shaped intermediate product after traveling through the electrolyte bath, it is important that residues of the electrolyte are removed completely from the wire-shaped intermediate product. For this purpose, after carrying out the electropolishing process, the intermediate product is advantageously cleaned; preferably, the intermediate product travels through another stationary cleaning device. This additional stationary cleaning device may have a plurality of cleaning stations, such as water baths, arranged one behind the other in the conveying direction of the intermediate product, in order to achieve a complete cleaning of the intermediate product and to prevent the electrolyte residues from being dragged to other processing stages.
It is also conceivable that, after carrying out the electropolishing process and preferably after traveling through the additional cleaning device, the intermediate product is conserved with a rust protecting agent in an appropriate conserving device; for this purpose, the intermediate product also advantageously travels through the conserving device, in order to obtain a continuously operating method.
As can be gathered from the above explanation of the invention, it is particularly useful if, for carrying out this method, the sawtooth wire is continuously pulled from an uncoiling reel, then travels first through a cleaning device designed for carrying out a mechanical cleaning, subsequently travels through the electrolyte bath, wherein the intermediate product essentially helically revolves through the electrolyte bath in order to achieve a long dwell time, the intermediate product travels after leaving the electrolyte bath through another cleaning device for removing electrolyte residues, then travels through a conserving device, and is then placed on and wound onto a coiling reel, wherein the conveying device required for this purpose is advantageously arranged between the conserving device and the coiling reel and includes two conveyor rollers between which the intermediate product is clamped.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.